The present invention is directed generally to processes for the preparation of aryl amine polycondensation polymers, and photoconductive imaging members thereof. More specifically, the present invention is directed to processes for the preparation of aryl amine poly(ethercarbonates) which can be selected as a charge transport layer in a layered photoconductive imaging member with a photogenerating layer and a supporting substrate. Aryl amine polymers usable in electrophotographic imaging processes are described, for example, in U.S. Pat. Nos. 4,801,517; 4,806,444 and 4,806,443, the disclosures of which are totally incorporated herein by reference. U.S. Pat. Nos. 4,806,443 and 5,028,687 disclose aryl amine poly(ethercarbonates), a solution polymerization process for the preparation of aryl amine poly(ethercarbonates), and the use of these polycarbonates in imaging systems.
The present invention relates to interfacial polymerization (IFP) processes for the synthesis of the aforementioned aryl amine poly(ethercarbonates). With interfacial polymerization instead of solution polymerization, there is enabled certain molecular weight polymers with narrow molecular weight distributions (MWD). Also, a significant improvement in the mechanical properties, including wear resistance is obtained with the products obtained with the processes of the present invention. For example, the wear resistance of imaging members containing the polymers of the present invention is improved by a factor of about 2 to 3 as compared to typical photoreceptor charge transport layers comprised of charge transporting small molecules, such as N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD), dissolved or dispersed in various polymers, such as polycarbonates like bisphenol A polycarbonate, including MAKROLON 5705.RTM.. One embodiment of the present invention is directed to an imaging member comprised of a supporting substrate, a photogenerating layer comprised of photogenerating pigments in contact therewith, and a charge, especially hole transport layer, comprised of the aryl amine poly(ethercarbonates) obtained with the processes as illustrated herein. The aforementioned imaging members are also useful in liquid development systems in that, for example, the members thereof can be resistant to cracking, crystallization, and brazing, and such imaging members are resistant to liquid developer components containing hydrocarbon type solvents, such as ISOPAR.RTM. and NORPAR.RTM., in that, for example, they retain their electrical and mechanical characteristics for extended time periods.
U.S. Pat. No. 4,806,443 describes a solution polymerization process for the preparation of aryl amine poly(ethercarbonates). Solution polycondensation involves the reaction of a dihydroxy aryl amine with a glycol bischloroformate in an appropriate solvent and in the presence of an organic base. The solution process yields polymers with relatively low molecular weights, such as from between about 40,000 to about 150,000 when a high purity dihydroxyaryl amine monomer is used. When the dihydroxyaryl amine monomer used contains small amounts of polyfunctional impurities, the polymer obtained can have a high molecular weight (M.sub.w over 200,000), however, the molecular weight distributions (M.sub.w /M.sub.n or MWD) are wide, of the range of 3 to 12. Materials with low molecular weights and/or wide molecular weight distributions suffer from poor mechanical performance in photoreceptor applications such as excessive wear and cracking. For purposes of increasing the molecular weight to about 200,000 to 300,000, there have been introduced during the polymerization reaction thereof crosslinking agents such as 1,3,5-benzenetricarbonyl trichloride, tri(4-hydroxyphenyl)ethane or 3,3', 3", 3'"-tetrahydroxytetraphenyl-benzidine. However, the use of crosslinking agents causes difficulties in controlling the molecular weight, results in high molecular weight distributions, and can cause problems in electrical properties of the polymer, as well as causing difficulties in processability due to increases in solution viscosities. To reduce the molecular weight distributions and thus improve the mechanical properties of these materials, fractionation is accomplished, generally by the selective precipitation of higher molecular weight polymer. This can result in poor yields of the desired polymer. These and other disadvantages are avoided, or minimized with the polycarbonates obtained with the processes of the present invention.
Photoresponsive imaging members are known, such as those with a homogeneous layer of a single material such as vitreous selenium, or composite layered devices containing a dispersion of a photoconductive composition. An example of a composite xerographic photoconductive member is described in U.S. Pat. No. 3,121,006, which discloses finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder.
Photoreceptor materials comprising inorganic or organic materials wherein the charge generating and charge transport functions are performed by discrete continuous layers are also known. Additionally, layered photoreceptor members are disclosed in the prior art, including photoreceptors having an overcoat layer of an electrically insulating polymeric material. Other layered photoresponsive devices have been disclosed, including those comprising separate photogenerating layers and charge transport layers as described in U.S. Pat. Nos. 4,265,990, the disclosure of which is totally incorporated herein by reference. Photoresponsive materials containing a hole injecting layer overcoated with a hole transport layer, followed by an overcoating of a photogenerating layer, and a top coating of an insulating organic resin are disclosed in U.S. Pat. No. 4,251,612, the disclosure of which is totally incorporated herein by reference. Examples of photogenerating layers disclosed in these and other patents include trigonal selenium and phthalocyanines, perylenes, and azo compounds, while examples of transport layers include certain aryl diamines as illustrated therein.
Layered photoconductive imaging members useful with liquid development systems are illustrated in U.S. Pat. Nos. 4,801,517; 4,806,443 and 4,806,444 mentioned herein.